Fuel-injection valve

ABSTRACT

Fuel injector ( 1 ), in particular, a fuel injector ( 1 ) for the direct injection of fuel into a combustion chamber of an internal combustion engine, includes an actuator ( 10 ) for actuating a valve needle ( 3 ), the valve needle ( 3 ) having on an injection-side end a valve-closure member ( 4 ) which forms a sealing seat together with a valve-seat surface ( 6 ), which is formed on a valve-seat member ( 5 ). Fuel channels ( 35 ) are arranged in a valve needle guide ( 31 ), connected to the valve-seat member ( 5 ) or designed as a single piece with it, in several rows ( 34, 34   a ) circumferentially in the valve needle guide ( 31 ), at least one row ( 34   a ) of fuel channels ( 35 ) being arranged, in the resting state of the fuel injector ( 1 ), above a guide line ( 33 ) of the valve-closure member ( 4 ).

BACKGROUND INFORMATION

[0001] The present invention relates to a fuel injector according to the preamble of the main claim.

[0002] From the German Patent Application 196 25 059 A1, a fuel injector is known, which has, in a flow path of the fuel from a fuel supply to an injection opening, several fuel channels whose cross-section determines the fuel quantity injected per time unit at a specified fuel pressure. In order to influence the fuel distribution in an injected fuel cloud, at least a portion of the fuel channels is oriented in such a way that the fuel jets emerging from them are injected directly through the injection opening.

[0003] It is especially disadvantageous in the fuel injector known from the above document that the fuel channels are arranged in a plane perpendicular to the flow direction of the fuel, and the openings thus are arranged on a circle around a valve needle guide connected to the valve-seat surface support. In this way, the fuel quantity flowing through the fuel injector cannot be metered accurately enough when the valve-closure member is lifted off of the sealing seat.

[0004] G8

[0005] Furthermore, the number of bore holes is not sufficient to generate an adequate homogenous fuel cloud that is sufficient to meet the stoichiometric requirements for full combustion. This is also additionally exacerbated by the large diameter of the fuel channels.

ADVANTAGES OF THE INVENTION

[0006] The fuel injector according to the present invention having the characterizing features of the main claim has, by contrast, the advantage that the adjustment of the fuel flowing through the fuel injector can be done with a high level of accuracy by the application of the slide valve principle with several rows of fuel channels arranged circumferentially.

[0007] By the measures listed in the dependent claims, advantageous refinements of the fuel injector specified in the main claim are possible.

[0008] It is also advantageous that the fuel channels axially offset from each other from row to row generate a homogenous mixture cloud.

[0009] By the arrangement of the fuel channels with a tangential component relative to the center line of the fuel injector, the fuel is given a swirl which also provides a good preparation of the mixture cloud.

[0010] The fuel channels may be inclined relative to a reference plane perpendicular to the center line of the fuel injector, whereby the hydrodynamic properties of the fuel channels are improved.

DRAWING

[0011] An exemplary embodiment of the present invention is shown in a simplified form in the drawing and explained in greater detail in the following description. Shown are:

[0012]FIG. 1 a schematic section through an exemplary embodiment of a fuel injector according to the related art,

[0013]FIG. 2 a schematic section through a first exemplary embodiment of the fuel injector according to the present invention in the area II of FIG. 1, and

[0014]FIG. 3 a schematic section along line III-III in FIG. 2.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

[0015] Before an exemplary embodiment of a fuel injector 1 according to the present invention is described in greater detail with reference to FIGS. 2 and 3, an already known fuel injector 1, equivalent in construction to the exemplary embodiments except for the measures according to the invention, will be explained briefly with reference to FIG. 1 with regard to its essential components, for better understanding of the invention.

[0016] Fuel injector 1 is designed in the form of a fuel injector for fuel injection systems of mixture-compressing, spark ignition internal combustion engine. Fuel injector 1 is especially suitable for direct injection of fuel into a combustion chamber of an internal combustion engine (not shown).

[0017] Fuel injector 1 includes a nozzle body 2, in which a valve needle 3 is arranged. Valve needle 3 is mechanically linked to a valve-closure member 4, which cooperates with a valve-seat surface 6 situated on a valve-seat member 5 to form a sealing seat. Fuel injector 1 in the exemplary embodiment is a fuel injector 1 that opens to the inside and which has an injection opening 7. Nozzle body 2 is sealed off by a seal 8 from external pole 9 of a solenoid 10. Solenoid 10 is encapsulated in a coil housing 11 and wound on a bobbin 12 which sits on the internal pole 13 of the solenoid 10. Internal pole 13 and external pole 9 are separated from each other by a gap 26 and are supported on a connecting piece 29. Solenoid 10 is excited via a line 19 by an electric current that may be supplied via an electric plug contact 17. Plug contact 17 is surrounded by a plastic sheath 18, which may be extruded onto internal pole 13.

[0018] Valve needle 3 is guided in a valve needle guide 14, which is designed in a disc shape. A matching adjustment disc 15 functions to adjust the lift. An anchor 20 is located on the other side of adjustment disc 15. This anchor is connected via a first flange 21 in a friction-fit manner to valve needle 3, which is connected to first flange 21 by a weld seam 22. A restoring spring 23, which in the model of fuel injector 1 presented here is pre-stressed by a sleeve 24, is supported on first flange 21.

[0019] A second flange 31, which is connected to valve needle 3 via a weld seam 33, functions as a lower anchor stop. An elastic intermediate ring 32, which rests on second flange 31, prevents rebounding when the fuel injector 1 is closed.

[0020] Fuel channels 30 a to 30 c, which conduct the fuel, which is supplied via a central fuel supply 16 and filtered by a filter element 25, to the injection opening 7, run in valve needle guide 14, in anchor 20, and on valve-seat member 5. Fuel injector 1 is sealed off by a seal 28 from a fuel line (not shown).

[0021] When fuel injector 1 is at rest, anchor 20 of restoring spring 23 is acted upon against its lift direction in such a way that valve-closure member 4 is held in a sealing contact on valve-seat surface 6. When solenoid 10 is excited, it generates a magnetic field, which moves anchor 20 against the spring force of restoring spring 23 in the lift direction, the lift being defined by an operating gap 27 located, in the rest position, between internal pole 12 and anchor 20. Anchor 20 takes flange 21, which is welded to valve needle 3, along with it in the lift direction. Valve-closure member 4 that is mechanically linked to valve needle 3 lifts away from valve-seat surface 6 and the fuel that is conducted via fuel channels 30 a to 30 c to injection opening 7 is injected.

[0022] If the coil current is turned off, after the magnetic field has sufficiently decayed, anchor 20 drops off internal pole 13 due to the pressure of the restoring spring 23, whereby flange 21, which is mechanically linked to valve needle 3, moves against the lift direction. Valve needle 3 is moved in this way in the same direction whereby the valve-closure member 4 is set on valve-seat surface 6 and fuel injector 1 is closed.

[0023]FIG. 2 shows, as a section of a detail, an exemplary embodiment of a fuel injector 1 according to the present invention. The section shown is indicated in FIG. 1 by II.

[0024] The exemplary embodiment shown in FIG. 2, of a fuel injector according to the present invention, has a valve needle guide 31, which is formed on an inlet side face 32 of valve-seat member 5. Valve needle guide 31 may be designed here in a single piece with valve-seat member 5 or, for example, be connected with valve-seat member 5 by welding, soldering, or similar methods. Valve needle guide 31 is designed as a hollow cylinder.

[0025] In the exemplary embodiment presented here, valve needle 3 has a ball-shaped valve-closure member 4. Valve-closure member 4 forms a sealing seat with valve-seat surface 6 formed on valve-seat member 5. Valve-closure member 4 is guided through valve needle guide 31, guide line 33 of valve-closure member 4 resting on an inner wall 38 of valve needle guide 31. In the area of guide line 33, i.e., between guide line 33 and the sealing seat, several rows 34 of fuel channels 35 are arranged in valve needle guide 31 and extend from a radially external side 36 of valve needle guide 31 to a radially internal side 39. In the resting state, in which valve-closure member 4 rests on valve-seat surface surface 6, in this embodiment, one row 34 a of these rows is arranged on the inlet side of guide line 33, while the other rows 34 are arranged between guide line 33 and valve-seat surface 6.

[0026] Fuel channels 35 may run here either perpendicular to a center line 37 of fuel injector 1 or inclined at an angle a relative to the orientation perpendicular to center line 37 in the downstream direction. The latter arrangement is more favorable hydrodynamically.

[0027] As soon as valve needle 3 is moved, when fuel injector 1 is actuated, opposite the flow direction of the fuel, fuel channels 35 of rows 34 are opened. Fuel flows from a radially external side 36 of valve needle guide 31 through fuel channels 35 in the direction of the sealing seat. In the starting phase of the opening operation, only those fuel channels 35 of those rows 34 are opened which are arranged on the downstream side of guide line 33 of valve-closure member 4. Fuel channels 35 of uppermost row 34 a, which in the resting state is arranged on the inlet side of guide line 33 of valve-closure member 4, remain closed at first. Once valve needle 3 has performed a specified partial lift, uppermost row 34 a is opened to allow flow.

[0028] By this two-part spatial arrangement of fuel channels 35, an expensive lift modeling of valve needle 3 can be avoided without impairing metering accuracy. Fuel channels 35 of rows 34 are arranged in such a way that a defined fuel quantity which is somewhat smaller than a required fuel quantity flows through. The flow through uppermost row 34 a of fuel channels 35 may be varied by changing the opening stop of valve needle 3 until reaching an exact fuel quantity. By corresponding adjustment of the lift of valve needle 3, exactly as much fuel flows through uppermost row 34 a of fuel channels 35, as is necessary in the context of the flow accuracy that is to be obtained.

[0029]FIG. 3 shows a schematic section along line III-III in FIG. 2, through valve needle guide 31 in the area of fuel channels 35. Fuel channels 35 of rows 34 are arranged axially offset from each other in the exemplary embodiment shown, in order to produce as homogenous a mixture cloud as possible. Fuel channels 35 may, however, also be arranged without axial offset. In order to achieve the required metering accuracy, fuel channels 35 have a very small diameter, for example, smaller than 100 μm, and in particular, smaller than or equal to 70 μm. The manufacture of these small-calibrated bore holes can be done by laser machining, for example.

[0030] Since fuel channels 35 have a tangential component relative to center line 37 of fuel injector 1 in order to produce a swirl, the cross-section of fuel channels 35 appears oval in FIG. 3. The orientation of the tangential components of fuel channels 35 in each row 34, 34 a may be in the same direction relative to the other rows 34, 34 a. The exemplary embodiment presented, of a fuel injector 1 according to the present invention, thus combines the preparation of the swirl with a refinement of the dosed fuel quantity.

[0031] The present invention is not limited to the exemplary embodiment shown and, for example, may also be applied for fuel injector 1 with piezoelectric and magnetostrictive actuators or any desired arrangements of fuel channels 33. 

What is claimed is:
 1. A fuel injector (1), in particular, for the direct injection of fuel into a combustion chamber of an internal combustion engine, having an actuator (10) for actuating a valve needle (3), the valve needle (3) having, on an injection-side end, a valve-closure member (4), which forms, together with a valve-seat surface (6), which is formed on a valve-seat member (5), a sealing seat, and having fuel channels (35), which are arranged in a valve needle guide (31) connected to the valve-seat member (5) or designed as a single piece with it, wherein the fuel channels (35) are arranged in a plurality of rows (34, 34 a) circumferentially in the valve needle guide (31), at least one row (34 a) of fuel channels (35) being arranged, in the resting state of the fuel injector (1), above a guide line (33) of the valve-closure member (4).
 2. The fuel injector according to claim 1, wherein the remaining rows (34) of fuel channels (35) are arranged between the valve-seat surface (6) and the guide line (33) of the valve-closure member (4).
 3. The fuel injector according to claim 1 or 2, wherein the valve needle guide (31) is formed on an inlet-side end face (32) of the valve-seat member (5).
 4. The fuel injector according to claim 3, wherein the valve needle guide (31) extends as a hollow cylinder from the end face (32) of the valve-seat member (5).
 5. The fuel injector according to claim 4, wherein the valve-closure member (4) is designed in such a way that in the area of the guide line (33) it rests on an inner wall (38) of the valve needle guide (31).
 6. The fuel injector according to one of the claims 1 through 5, wherein the fuel channels (35) of the circumferential rows (34, 34 a) are arranged axially offset from one another.
 7. The fuel injector according to one of the claims 1 through 6, wherein the fuel channels (35) have a tangential component relative to a center line (37) of the fuel injector (1).
 8. The fuel injector according to claim 7, wherein the tangential components of the rows (34, 34 a) are oriented in the same direction.
 9. The fuel injector according to one of the claims 1 through 8, wherein the fuel channels (35) are formed in a plane perpendicular to the center line (37) of the fuel injector (1).
 10. The fuel injector according to claim 9, wherein the fuel channels (35) are inclined at an angle α relative to the orientation radial to the center line (37). 